The use of prosthetic liners for below knee amputees is well known from the prior art. A prosthetic liner is worn between the amputation limb and the prosthesis socket, carrying the lower leg portion of the prosthesis. The liner is worn directly on the amputation limb. At the closed distal end of the liner body the liner is provided with means for connecting the liner to the prosthesis socket. These means might, for example, be threaded inserts, which may be molded into the polymer-like liner material, in particular by injection molding.
Since the liner usually is the only part of the prosthesis getting in direct contact with the skin of the amputee and the liner is usually worn the whole day, it is important to make the liner as comfortable to wear as possible. The liners might be, for example, constructed either of a fabric impregnated with silicone or another polymer-like material or from the polymer-like material only.
From U.S. Pat. Nos. 6,440,345 B1 and 6,918,936 B2 a liner is known, which comprises a knee part having a pre-flexed angle. This is also known from U.S. Pat. No. 5,888,216. Compared with the straight tubular shape liner, this pre-flexed angle minimizes the wrinkling behind the knee, especially when the knee is bent. In addition it increases the range of motion of the knee joint and is more comfortable to wear when sitting.
Since the diameter of the amputation limb of the person usually decreases towards the distal end of the amputation limb, the distal part of the liner according to U.S. Pat. No. 5,888,216 is tapered. This leads to a better fit and a more homogeneous distribution of pressure at the amputation limb of the person.
From US 2010/0016993 a liner is known, which also shows a knee part, in which a strip or a tendon is attached to urge the elastomeric material in this region of the tubular liner body to contract. This strip or tendon is, for example, of silicone having a higher durometer hardness value than the material of the liner body and may be, for example, integrally molded with the knee portion of the tubular liner body.
In order to provide a perfect fit of the liner at the residual limb of the person it is possible to use a fully individualized liner or to individualize a standard liner, as, for example, is known from WO 2009/109182. Since the construction of an individual liner is time-consuming and expensive it is much cheaper and faster to provide some standard liners which may be available in different sizes and to use these standard liners for each amputation limb.
Unfortunately, amputation limbs are shaped very individually. When a standard liner is used it is possible that cavities occur between the amputation limb of the person and the liner. This may lead to swelling or chafing at the residual limb. In order to prevent at least most of these cavities from occurring between the liner and the residual limb it is known, for example, from US 2005/0240283 A1 to insert some cushions into the liner. This leads to a more homogeneous distribution of pressure at the surface of the amputation limb covered by the liner.
At the distal end of the liner there is usually a means for connecting the liner to the remaining parts of the prosthesis. Silicone liners particularly utilize a hard unyielding material such as aluminum or thermoplastics such as polycarbonate or polyamids as a shuttle screw housing for fixing the lower leg portion of the prosthesis. The said means may also be a screw housing or a threaded insert which might be molded into the material of the liner body. In order to prevent these hard materials from being felt by the wearer of the prosthesis liner, the thickness of the molded polymer-like liner material is considerably enhanced at the closed distal end of the liner body.
In order to increase the wearing comfort of the prosthesis even further, it is known to insert some cushions into the prosthetic socket, which is to be fixed to the liner. Since the prosthetic socket is made from a rigid material, this may lead to bruising and chafing and hence to discomfort and pain.
These cushions are usually positioned at an inner surface of the prosthetic socket. This leads to dirt pockets making the cleaning of the prosthetic socket difficult and time-consuming. In addition it is difficult to position these cushions at the inner surface of the prosthesis socket exactly. This might lead to wrong positions of the cushions so that the desired cushioning effect is not realized or at least is not realized at the desired locations at the amputation limb. This again leads to chafing, pressure points, swelling and pain.